Electronic state spectroscopy of C2Cl4

Abstract The VUV spectrum of C 2 Cl 4 is reported in the energy range 3.8–10.8 eV (325–115 nm). Several photoabsorption features are observed for the first time, including a very weak low-lying band which is provisionally attributed to a π → π∗ triplet transition. Recent ab initio calculations of the molecule’s electronic transitions [S. Arulmozhiraja, M. Ehara, H. Nakatsuji, J. Chem. Phys. 129 (2008) 174506] provide the basis for the present assignments below 8.5 eV. An extended n dπ series is proposed to account for several higher-energy Rydberg bands. The identification of vibrational structure, dominated by symmetric C C and CCl 2 stretching in excitations from the HOMO, largely agrees with previous spectroscopic studies. The present absolute photoabsorption cross sections cover a wider energy range than the previous measurements and are used to calculate UV photolysis lifetimes of this aeronomic molecule at altitudes between 20 and 50 km.